QT20n Z axis servo alarm 14

Hello, I have been seriously enjoying my QT20n......but with the onset of the really hot weather (100 or so) I have been getting a Zaxis Drive alarm.

Everything will work fine in the morning, but once the temp gets over 95ish I will get the drive alarm.

It is the 4th LED down on the TRA 41a drive. The book says it is a fin overheat alarm and will disable the drive at 80 (180F) degrees C and reenable at 55C (130F). I am a very light user of the machine, and there is no way its getting that hot.

I got the error this afternoon, and just went home. I came back a few hours later, and the machine had cleared the alarm. I finished running one part for about 3 minutes, then spent the next 15 minutes writing a new program. Just as i finished the program, I got the alarm again.

I immediately pulled out the drive, and could feel no heat above ambient on the heat sink. It was about 97 degrees at that time.

I see a device on the heat sink that is probably the temperature sensor. It changes resistance when I put a hair dryer on the heat sink. I guess it's a type of thermistor. Seems to range between 54 and 59ohms when heated.

The alarm was Z Drive Axis 14, I believe.

Just wondering if anyone has dealt with this before?

Some time tomorrow, I suppose I will check the resistance on the x drive to compare.

Its definitely not shutting off because of excessive heat generated by the drive itself, as it's probably not over ambient by more than 10. degrees F.

Mike

Mike,

The temperature sensor may be bad? You might try "hot-wiring" the sensor (no pun intended), to prevent it from tripping the overheat circuit.

Also, make sure the fan on the drive fins is working.

I agree, the drive should be almost too hot to touch if it were legitimately shutting down because of an overheat.

The TRA-31 (X-axis) and TRA-41 (Z-axis) drives are on Ebay all the time. Might be good to pick up a spare??

Good luck,

Greg

I agree with that idea......I just don't know how to go about it yet.

The sensor does not seem to be an open or closed type like I hoped. It appears to be variable resistance. I think it probably operates as a voltage divider with another fixed resistor to give an analog voltage. That would explain the offset on/off temperature. If that's true, I should be able to alter the fixed resistor if I can find it.

I'm going to do some analyzing of the X drive for comparison tomorrow. I suppose I could swap out the sensors to make sure that it is the problem.

The sensor is three wires......which is also confusing. Not sure what the extra wire is for. It looks like it goes to run the fan (AC).....which is working fine.

Mike

I pulled out what i thought was the temp sensor, and was able to get the numbers off of it. It wasn't a temp sensor at all.....lol.....but a transistor. It didn't look like any temperature sensor I had seen pictures of......but I couldn't see any thing else on the heat sink that could have been what I was looking for.

I looked again, and there it was......right in front of my eyes. I don't know how I overlooked it before. This one had only two wires. I checked across them and found no resistance. I heated it with the hair dryer for about 3 seconds, and it changed to an open circuit.

I jumpered the sensor and put the thing back into the machine. I ran it for a few hours this afternoon in the 97 degree heat with no trouble.

I reached my hand around to the back of the drive heat sink to get a feel for the temp, and it was warm.....maybe 110 degrees.

I'll order another sensor, but in the meantime.....I'm just gonna run it like it is.

I absolutely love this machine.

Thanks for the advice, Cat.

Mike

michaelthomas said:

I absolutely love this machine.

Thanks for the advice, Cat.

Mike

Click to expand...

You make us proud, son.

Thanks, Phil.